Yoshihiro Tanaka. Osaka Museum of Natural History, Nagai Park 1-23, Higashi-Sumiyoshi-ku, Osaka, 546-0034, Japan tanaka@mus-nh.city.osaka.jp and Division of Academic Resources and Specimens, Hokkaido University Museum, Kita 10, Nishi 8, Kita-ku, Sapporo, Hokkaido 060-0810 Japan and Numata Fossil Museum, 2-7-49, 1 Minami, Numata Town, Hokkaido, 078-2202 Japan

Yoshi Tanaka is a curator at Osaka Museum of Natural History, Japan and also a researcher at Hokkaido University Museum. He works on the morphology and phylogeny of marine mammals (dolphins, porpoises, whales and walruses) from Japan, Ecuador and New Zealand. This paper is a part of his research project of an ancient bay in Osaka.

Hiroyuki Taruno. Osaka Museum of Natural History, Nagai Park 1-23, Higashi-Sumiyoshi-ku, Osaka, 546-0034, Japan hiroyukitaruno@gmail.com

Hiroyuki Taruno is a former curator and currently a researcher of Osaka Museum of Natural History, Japan. He has researched on local geology, vertebrate paleontology and osteology for half a century. His long-term research activities have expanded his interests on taxonomy, paleogeography and evolution of elephants, deers, carnivoras and crocodiles from the Pliocene to Holocene.